From: "Laurence J Howell
In looking at my LF Inverted L, and specifically the 3 wire top loading
wires - I've a couple of questions...
1. I see a recommendation that the vertical part of the Inv L aerial
wire(s) should be a single wire (ZL recommendation), or if not then three
or how many wires should converge to a single point at the bottom. Why is
a
single wire recommended over a multiple? Em thinking losses into nearby
objects? Wouldn't a multiple vertical wire feed increase "good non lossy"
C and increase Ra?
Yes, it will increase the C to ground, but you want this as high as
possible. Three wires all the way up will give you C near the bottom which
is bad news.
2. Ive seen a large amount of schematics both for commercial and ham top
loading.of T and L's ...Say for a three wire top loading spaced 1m apart -
should the wires at the far/near end all be shorted together or left open?
Does this affect the total cap either way, or is it just for electrical
"circuit" stability?? Does it make any difference if they are shorted at
any point along the top?? Is there a recommendation which proves open
versus short is better ?
I have done some crude experiments and have found little difference.
However, I have found that the more you join together, the less there is to
fall down if a single support rope fails. My three top wires are each
supported by their own insulators and polyprop rope, but are shorted at the
ends. If any two ropes break, the third will still support the antenna via
the shorting wires (the top section will be bent but will work, at slightly
reduced efficiency).
Mike, G3XDV
http://www.lf.thersgb.net
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